On The Performance of Mechanical Shock Indicators

Abstract

Cost‐effective mechanical shock indicators are widely used to warn if a package has been subjected to a shock event during distribution. Such devices are an important part of the quality control and monitoring process during the distribution of fragile products. As the distances over which goods are transported continues to increase, so does the reliance on such devices to ensure that, should product damage occur due to excessive shocks during distribution, some evidence of the cause is available. However, there is a growing number of cases where false or misdetection has been reported producing misleading or confusing information hence loss of confidence in the data. This paper presents an experimental investigation into the actual response characteristics of three commercially available mechanical shock indicators (beam type, liquid‐in‐glass tube type and magnetic type). Specifically, this paper addresses the influence of shock pulse duration on the performance of shock indicators as well as evaluating the devices' repeatability across a broad range of shock pulse durations. Included in the paper are descriptions of the specially adapted test apparatus which employs a pneumatic rubber bladder to generate half‐sine shock pulses of varying durations by adjusting the bladder pressure. Results from experiments show that each device is sensitive to shock magnitude as well as shock duration to varying extents. The paper makes recommendations on the use of the devices, and the findings highlight the need for establishing the shortest pulse duration experienced by any packaged product by means of drop tests before employing the devices. Copyright © 2017 John Wiley & Sons, Ltd.